As a valve device having a cutoff valve for a fuel tank and detection means for a full tank, there is a valve device shown in Patent Document 1. This device comprises an evaporator opening in an upper portion of a housing where a float valve is housed, and a fuel opening in the lowest portion. When a fuel liquid surface reaches the fuel opening by fueling, the float valve is elevated and blocks the evaporator opening. Thereby, the fuel liquid level inside a filler pipe is elevated, and the fueling is stopped by allowing a sensor of a fueling gun to detect the full tank. In the upper portion of the housing of this device, a through-hole is provided. Once the fueling is stopped, due to airflow through this through-hole, a pressure inside the housing and a pressure inside the tank are attempted to be balanced, and the fuel liquid level inside the housing declines, so that the float valve descends. This allows the airflow through the through-hole and the evaporator opening to be carried out, so that the pressure inside the tank declines, and the fuel liquid level inside the filler pipe also declines so as to create a possible state for additional fueling. However, in the device shown in Patent Document 1, since only such through-hole is simply provided in the housing, the float valve could easily descend immediately after the detection of the full tank. If the fuel liquid level inside the filler pipe declines immediately after the detection of the full tank, an automatic stop of the fueling gun is released, and additional fueling becomes immediately possible, so that overfilling occurs.